drm/amd/display: Optimize OLED T7 delay

[Why]
Driver doesn't need T7 delay for OLED panels, since it doesn't control
power sequence.

[How]
This delay can be skipped to optimize resume times.

Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Charlene Liu <charlene.liu@amd.com>
Reviewed-by: Swapnil Patel <swapnil.patel@amd.com>
Acked-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Agustin Gutierrez <agustin.gutierrez@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>